Dear Alyssa
I guess you are talking about an oral IR formulation, right?
ISCV are not carved in stone, there will always be a certain variability. However, big differences hint on differences in study performance and/or quality of formulations. It is reasonable to assume that the ISCV in the pivotal study will be similar to the pilot study if you use the same CRO (study procedure performance), the same test formulation vs. the same (batch of) reference product and the same bioanalytical method. If costs do not matter you can of course follow the suggestion of the CRO to go for 4 way crossover, replicate design, with ratio 90-111%, ISCV = 35-40%.
I hope this helps